Determination of Major-to-Trace Minerals and Polyphenols in Different Apple Cultivars

Abstract

The aim of this study was to investigate the concentration level of some major-to-trace elements and toxic minerals and polyphenols (catechin, epicatechin and quercetin) in fruits belonging to different apple cultivars (‘Auriu de Cluj’, ‘Florina’, ‘Generos’, ‘Golden Delicious’, ‘Prima’, ‘Productiv de Cluj’ and ‘Starkrimson’), under specific climate conditions to northwestern Romania. The apple minerals were determined by the inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES) after a preliminary, microwave-assisted, acid digestion. The polyphenols were determined by high performance liquid chromatography (HPLC) with MS/MS detection. According to the obtained results, the edible part of the apple contains many minerals with high relative nutritional value (RNV). The major minerals (Na, K, Ca, Mg and P), minor elements (Cu, Fe, Mn, Sr and Zn) and toxic trace elements (Cd, Cr and Pb) were comparatively identified and quantified. It was found that K (31976 mg/kg) was predominant among the major elements, while Fe (3.68 mg/kg) and Cu (3.57 mg/kg) were comparable. The toxic trace metals (Cd, Cr and Pb) were below the limits of detection (0.01, 0.10 and 0.01 mg/kg, respectively) and did not determine any health risk to consumers. The main polyphenols composition (catechin, epicathechin, quercetin) differs slightly among different cultivars. In ‘Idared’ and ‘Jonathan’ cultivars, the investigated polyphenols are in higher quantities comparing to the others. In all investigated apple cultivars, quercetin was proved to be the major polyphenol, followed by epicathechin and catechin. These results suggest that, regarding only the investigated polyphenols, ‘Idared’ and ‘Jonathan’ cultivars have the highest antioxidant character in all investigated genotypes.